The present invention relates to the field of the quantitative evaluation of energy or of power conveyed and imposed by radiofrequency radiations, particularly for the regulation and control of a process for treatment using heating by radiofrequency radiation, in particular microwaves, and has for its object a radiometer adapted to measure the thermal noise emitted by a body or a portion of a body so as to determine the mean temperature thereof, in a precise and continuous manner.
There already exist different types of radiometers based on the principle of the evaluation of the energy of the thermal noise emitted by a body to determine the temperature thereof.
This evaluation is always effected, in these known radiometers, by comparing the energy of the signal of thermal noise detected by an antenna disposed on or in the body whose temperature must be determined, with the energy of one or several signals of thermal noise delivered by at least one reference source, whose temperature or temperatures is or are known, as well as the energy of the signal reflected by a radiofrequency short circuits if desired.
However, the determination and evaluation of the different mentioned signals is done in an alternating and cyclical manner, which does not permit indicating in a continuous manner the instantaneous temperature of the body in question. Thus, these existing radiometers permit only displaying, with cooling, of the value at regular intervals of generally more than 5 seconds, a value of the temperature offset in time, which does not correspond to the actual value of the temperature at the moment of display, but at that which was taken several seconds previously.
These radiometers therefore do not permit precisely following in real time the temperature, as is necessary for example for the regulation of a process for treatment by hyperthermia or microwave thermotherapy and in which the occurrence of abnormal heating or the exceeding of a threshold value must be noted as quickly as possible, which is rendered relatively delicate because of the high thermal loss and dissipation of living tissue.
Moreover, these existing radiometers do not take into account as desired ranges of frequencies polluted by parasitic emissions (radars, microwave ovens, radiotelephones) which interfere or superpose themselves on the thermal noise signals to be measured and as a result render false the measurements of temperature based on the evaluation of the energy or the power of the signals detected by the measuring antenna.
Moreover, these existing radiometers require long and fastidious calibration phases, which it is often necessary to repeat several times for a single set of measurements.